EP3213993B1 - An aircraft provided with a buoyancy system, and a buoyancy method - Google Patents

Description

The present invention relates to an aircraft equipped with a buoyancy system, as well as a buoyancy method.

Therefore, the invention lies in the technical field of buoyancy systems for landing and stability afloat of an aircraft, and more particularly a rotary wing aircraft.

Such a buoyancy system contributes to the floatation and stability of an aircraft following a landing. The buoyancy system can be used for example following a ditching, to allow evacuation of the occupants of this aircraft. All devices dedicated to passenger missions in maritime areas are equipped in principle with such a buoyancy system.

Aeronautical certification regulations specify that an aircraft must be able to land and be stable on the water with its buoyancy system. Stability must be proven for free surface water states and wind levels that are defined in these certification regulations.

These water-free surface states are also called "sea state", and apply to any liquid surface. The term "landing" covers the position of an aircraft on any water-free surface, whether on the sea or on a lake, for example. Certification regulations require the stability of an aircraft with a particular sea state.

A buoyancy system may include floats.

The floats are fixed on either side of a cell of the aircraft. The term "cell" refers to a portion of the aircraft housing a cockpit, or even a cabin and a cargo hold.

For example, floats are fixed in a lower part of the aircraft. The floats are then optionally attached to a landing gear carrying the cell, or to an outer wall of the cell.

Some flotation systems include inflatable floats whose deployment is controlled either by the pilot and / or co-pilot, for example, or by an automatic trigger including through one or more sensors (s) immersion. These floats may comprise, for example, bags inflated by a deployment means.

In addition, the floats can be paired to optimize the stability of the aircraft on the water. Therefore, the floats of a pair can be arranged on either side of the cell of the aircraft.

Such a flotation system is satisfactory to ensure the stability of the aircraft with a level 4 sea state in particular.

However, in an extremely turbulent sea with a sea state that is much higher than the sea state required by certification regulations or under a high intensity wave, floats may sink under the liquid surface when the aircraft has a very important roll angle.

If the center of gravity of the aircraft is no longer at a space separating two floats of a pair of floats, the aircraft can capsize.

The document US 2013/0327890 presents a helicopter with floats carried by fins. These floats are substantially arranged at mid-height of the helicopter, and notably substantially at mid-height of the cabin in accordance with the Figure 2c of this document US 2013/0327890 .

To limit the risk of capsizing, the floats can be connected to a cell by an elastic means. The document US 2015/0217862 presents an aircraft of this type.

The document FR 2,994,686 proposes to bind floats to a fuselage by a connecting device allowing a transverse displacement of each float relative to the fuselage.

The documents FR 3011817 and FR 3017107 are also known.

The documents JP H04 63800 , US 2010/044506 and US 3321158 are also known.

The present invention therefore aims to provide an aircraft with optimized stability following a landing.

According to the invention, an aircraft is provided with a cell which extends longitudinally along an anteroposterior plane, the cell extending transversely from a left side to a right side and in elevation from a bottom to a Mountain peak.

The aircraft comprises a buoyancy system, this buoyancy system being provided with at least one pair of two floats, two distinct floats of a pair being arranged transversely on either side of the anteroposterior plane.

Each float is movable in elevation from a lower position to a higher position, the center of gravity of each float being present in a higher plane perpendicular to the anteroposterior plane in the upper position and in a lower plane in the lower position, the lower plane being parallel to the upper plane and being located under the upper plane when the aircraft has a zero roll angle, the buoyancy system comprising for each float a blocking system to block each float by default in the lower position and to block in a predetermined condition the floats present on one side of the aircraft in the upper position.

The expression "in a predetermined condition" means that all the floats present on the left side or all floats present on the right side are released to reach their higher positions when a predetermined condition occurs.

The term "blocking system" designates a system capable of blocking each float in a lower position or in an upper position according to the predetermined condition.

The expression "single-sided floats" refers either to the floats present on the left side of the aircraft or to the floats present on the right side of the aircraft.

Therefore, the aircraft is provided with at least one pair of floats. The floats can take the form of structural or inflatable floats. In the context of inflatable floats, the floats can be inflated before, during or after landing by applying the usual deployment methods.

Whatever the nature of the floats and their mode of inflation if any, the floats are all maintained in their lower position following the landing. The aircraft then behaves afloat in much the same way as a conventional aircraft. The aircraft is in a position called for convenience "conventional position".

By cons, when the predetermined condition occurs, the locking system releases each float present on the left side of the aircraft or each float present on the right side of the aircraft. The floats that are released by the blocking system are called "floats released" for convenience. Each float released then moves to reach its upper position. For example, the buoyancy force exerts an effort on each float released allowing the displacement of these floats released in elevation along the cell.

The blocking system then blocks each float released in its upper position to make irreversible the displacement of the float released, at least without human intervention.

The displacement of each float present on one side of the aircraft induces rollover of the aircraft. The aircraft tilts towards the side of the aircraft carrying the released floats which are in the upper position.

The aircraft is thus in a more stable position on the so-called convenience water "maximum stabilization position".

In addition, the displacement of each float released is carried out gradually. As a result, the tilting of the aircraft from the conventional position to the maximum stabilization position is smoothly performed, which may tend to limit the stress of the occupants of the aircraft.

Furthermore, in the maximum stabilization position, the aircraft has a non-zero roll angle, but is not totally reversed. As a result, a volume of the cabin occupied by individuals can stay out of the water to allow occupants' breathing.

To take advantage of this aspect, the upper positions of each float can be studied to maintain the head of each occupant sitting on a seat out of the water, at least from a size limit of an occupant and in the absence capsizing.

In addition, even if the aircraft turns over in the presence of a particularly severe sea state, the aircraft will nevertheless have an inclination tending to maintain a pocket of air within the cabin.

The displacement of each float present only on the same side of the aircraft is not obvious. Indeed, this displacement induces an increase in the roll angle of the aircraft which does not seem reasonable because part of the cabin is then immersed.

However, the applicant notes that the stability of the aircraft on the water is then maximum. In addition, this roll tilt makes it possible to keep part of the cabin out of the water to allow the breathing of the occupants of the aircraft.

The aircraft may further include one or more of the following features.

For example, the cell extending in elevation from a lower part including the bottom to an upper part including the top, the lower position is located in the lower part of the aircraft while the upper position can be located in the part superior of the aircraft.

As a result, a float in its lower position is then located at the bottom. When the roll angle of the aircraft is zero, the float is located under a median plane separating the lower part of the upper part, this median plane being a plane which is perpendicular to the anteroposterior plane and which is defined by a transverse axis and an elevation axis of the aircraft.

By cons, the float is located at the upper part in its upper position. When the roll angle of the aircraft is zero, the float is then located above the median plane.

Furthermore, the buoyancy system may be provided for each float with at least one slider slidably mounted relative to a rail, each rail extending in elevation, from the lower part to the upper part, each slider being attached to a slider. corresponding float.

Each float is movable in elevation from a lower position to an upper position by sliding each slide attached to the float along a rail

The locking system may then include locks to lock the slide relative to the corresponding rail.

Each slide may take the form of a fitting carrying at least one caster which slides in a rail. The slider can then move along the rail to allow movement of the float.

Optionally, the buoyancy system is provided for each float of two slides mounted respectively sliding relative to two rails, each rail extending in elevation, from the bottom to the top, each slide being attached to a corresponding float.

Therefore, the rails can for example be installed in a door frame.

Furthermore, the locking system may comprise at least one lock called "lower lock" for holding a float in the lower position, the locking system comprising at least one lock called "upper lock" for holding a float in the position upper, the blocking system comprising a processing unit connected to an activation system, the processing unit controlling each lower lock to allow movement of a float from the lower position to the upper position on request of the system of activation, the upper lock having the function of rendering said displacement irreversible without manual action of an individual on each upper lock.

The expression "processing unit" designates a system able to control at least one lock to open or close this lock.

The term "activation system" refers to a system capable of generating a signal transmitted to the processing unit to indicate that at least one lock must be open.

Following the landing, the lower locks keep each float in its lower position.

As soon as a predetermined condition occurs, the activation system sends a signal to the processing unit which opens the lower latches present on one side of the aircraft. Each float associated with an open lock is then released, and moves to its upper position. At least one upper lock then blocks the float in its upper position.

In addition, a predetermined condition may arise when a movement order of each float present on one side of the aircraft is given by a pilot.

The term "pilot" is to be interpreted broadly by referring to an individual, for example an individual present in the aircraft.

Therefore, the activation system comprises a control member operable by a pilot allowing a pilot to choose to keep each float in its lower position or to allow the displacement of each float present on one side of the aircraft to his superior position.

A predetermined condition may occur when the aircraft reaches a threshold roll angle. Therefore, the activation system comprises a measurement system that measures a roll angle of the aircraft.

This measurement system communicates with the processing unit to require the displacement of at least one float as soon as a threshold roll angle is reached.

Furthermore, at least one lock may comprise a rotary valve articulated to the cell in order to rotate to project from a coating of the aircraft in a locking position in order to block the float or to be retracted at least partially in said coating in an unlocking position to unlock the float.

Such a lock is relatively simple and lightweight.

The rotary valve may be provided with an inclined face and a flat face, the inclined face presenting a first acute inclination with respect to a direction of displacement extension of the float from the lower position to the upper position, the plane face having a second inclination with respect to the extension direction which is greater than the first inclination.

The flat face may be substantially perpendicular to the direction of travel.

In addition, a lock may comprise a spring exerting a force on the valve to tend to hold the valve in the locking position.

Furthermore, the valve may comprise a stop for stopping a rotation of the valve from the unlocking position to the locking position when this locking position is reached.

To be open on request by a pilot, a lock may further include an electrical immobilizer cooperating by interference pattern with the valve to prevent or allow a rotation of the valve on request of a processing unit.

The immobilizing member may for example comprise an electric strike or a latch movable by an electrically operating means.

In another aspect, when the aircraft comprises portholes, a float may be located at least partially under a window in the lower position and at least partially above the window in the upper position to not completely close said porthole.

The expression "under a porthole" means that the float has a section protruding under the window so as not to completely close the porthole. Similarly, the expression "located above the window" means that the float has a section protruding above the porthole so as not to completely close the porthole.

As a result, the window is not completely closed by a float when the float is in its lower position or its upper position. The porthole can then be used as an emergency exit.

In addition to an aircraft, the invention relates to a method applied by this aircraft.

The invention therefore relates to a buoyancy method for floating an aircraft provided with a cell that extends longitudinally along an anteroposterior plane, the cell extending transversely from a left side to a right side and in elevation from a bottom to a top, the aircraft comprising a buoyancy system, the buoyancy system being provided with at least one pair of floats, two external floats of a pair being arranged transversely on either side of said plane anteroposterior outside the cell.

• chaque flotteur d'une paire est rendu mobile en élévation d'une position inférieure vers une position supérieure, chaque flotteur étant attaché à au moins un coulisseau (45) qui est rendu coulissant par rapport à un rail (41) pour permettre le déplacement du flotteur de la position inférieure vers la position supérieure,
• on maintient chaque flotteur par défaut dans une position inférieure, et
• lorsqu'une condition prédéterminée survient, on dispose tous les flotteurs présents d'un unique côté de l'aéronef dans la position supérieure.

According to this method:

• each float of a pair is made movable in elevation from a lower position to an upper position, each float being attached to at least one slider (45) which is slidable relative to a rail (41) to allow movement of the float from the lower position to the upper position,
• we keep each float by default in a lower position, and
• when a predetermined condition occurs, all the floats present on one side of the aircraft in the upper position are arranged.

In particular, it is possible to have the floats present on one side of the aircraft in the upper position at the request of a pilot or when an angle of roll of the aircraft reaches a predefined threshold.

In calm sea conditions, the floats may remain in a lower position.

• la figure 1, un schéma présentant un aéronef muni d'un système de flottabilité selon l'invention,
• les figures 2 et 3, des vues transversales schématiques de cet aéronef illustrant respectivement des flotteurs dans une position inférieure et dans une position supérieure,
• les figures 4 et 5, des figures illustrant un flotteur coopérant avec un coulisseau et un rail,
• les figures 6 à 8, des schémas illustrant des verrous aptes à maintenir un flotteur dans une position,
• les figures 9 à 11, des schémas explicitant le fonctionnement de l'invention.

The invention and its advantages will appear in more detail in the context of the description which follows with examples given by way of illustration with reference to the appended figures which represent:

• the figure 1 , a diagram showing an aircraft equipped with a buoyancy system according to the invention,
• the Figures 2 and 3 schematic transverse views of this aircraft respectively illustrating floats in a lower position and in an upper position,
• the Figures 4 and 5 , figures illustrating a float cooperating with a slider and a rail,
• the Figures 6 to 8 , diagrams illustrating locks able to maintain a float in a position,
• the Figures 9 to 11 , diagrams explaining the operation of the invention.

Note that three directions X, Y and Z orthogonal to each other are shown in the figures.

The first direction X is called longitudinal. The term "longitudinal" relates to any direction substantially parallel to the first direction X.

The second direction Y is called transverse. The term "transverse" is relative to any direction substantially parallel to the second direction Y.

Finally, the third direction Z is said in elevation. The expression "in elevation" relates to any direction substantially parallel to the third direction Z.

The figure 1 presents an aircraft 1. This aircraft can notably be a rotorcraft.

This aircraft 1 comprises a cell 2 extending longitudinally from a front end 3 to a rear end 4 along an anteroposterior plane 100. Optionally, the anteroposterior plane is a plane of symmetry of the aircraft.

In addition, the cell 2 extends transversely from a left side 5 to a right side 6 on either side of the anteroposterior plane 100. As a result, the cell 2 comprises an outer coating called simply "coating 550" which materializes a left flank 600 of the cell and a right flank 500 of the cell.

In this context, the term "left" refers to the parts of the aircraft present on the left side of the aircraft, and the term "right" refers to the parts of the aircraft present on the right side 6 of that aircraft. The term "left" therefore designates the parts of the aircraft present on the left 5 of the anteroposterior plane 100, and the term "right" designates the parts of the aircraft present on the right of this anteroposterior plane 100.

In addition, the cell extends in elevation from a bottom 700 of a lower part 7 of the cell to an apex 800 of an upper part 8.

The lower part 7 is conventionally provided with a landing gear, while the upper part 8 can carry a rotor 9 participating in the lift or propulsion of the aircraft. The lower part may include a boat bounded in particular by the floor of an internal space and the coverings of the cell.

The upper part can therefore carry a rotor 9 in the context of a rotorcraft. This rotor 9 is rotated by at least one motor 115 through a power transmission box 120. This engine 115 may be a turbine engine equipped with an expansion turbine secured to a working shaft, the shaft working piece being connected by a mechanical chain to the power transmission box 120.

The lower part can then represent the lower half of the cell while the upper part represents the upper half of this cell.

Furthermore, the interior INT of the cell 2 has hollow internal spaces which are delimited by the coating 550 and various partitions. Each internal space then represents a compartment which extends in particular in elevation of a base called "floor" for convenience to a ceiling. Optionally, the ceiling of one compartment may represent the floor of another compartment.

In addition, this aircraft 1 is further provided with a buoyancy system 20 according to the invention to be able to fish.

Such a buoyancy system may include a system blowing air into the cell following a landing. Such system may comprise at least one pump sucking air outside the aircraft to reinject this air into the cell. The cell can be airtight, especially in its lower part to form an airtight pocket.

In addition, the buoyancy system 20 is provided with at least one pair of floats 25.

Each pair of floats comprises two floats 25 arranged transversely on either side of the cell 2 of the aircraft. The floats 25 of a pair of floats are then placed on either side of the anteroposterior plane 100, and for example outside the EXT of the cell 2. The expression "arranged outside EXT of the cell 2 Means that the floats are at least partially deployed outside the cell 2 following a landing.

Thus, a float 25 called "float 31" is disposed on the left side 5 of the aircraft, while a float 25 called "right float 32" is disposed on the right side 6 of the aircraft.

Floats 25 of a pair may be arranged symmetrically on either side of the plane anteroposterior plane 100 of symmetry of the aircraft in a stable position of the aircraft.

For example, the aircraft has one or even two pairs of floats 25.

Moreover, each float 25 may comprise an envelope 30 which floats on the water, this envelope trapping a gas for example. The length of the envelope then represents a dimension of this envelope in a longitudinal direction, the width of the envelope represents a dimension of this envelope in a transverse direction, and the thickness of the envelope represents a dimension of this envelope according to a direction in elevation.

This envelope 30 may be a structural envelope made of composite materials, metal, plastic ...

However, the envelope 30 may be an inflatable.

Therefore, at least one float 25 is inflatable. Optionally, all the floats 25 are inflatable. As a result, the inflatable floats are deflated outside the landing phases. The inflatable floats can in particular be folded in a space provided for this purpose before inflation.

Under these conditions, the buoyancy system includes an inflation system for inflating each inflatable float. This inflation system comprises at least one inflator 35 for inflating the inflatable floats. Each inflator may include an electric, explosive, pneumatic or chemical inflator.

For example, but not exclusively, an inflator 35 is connected to a plurality of floats 25. figure 1 illustrates on the contrary an inflation system comprising several inflators 35. Optionally, the inflation system comprises at least one inflator 35 per float.

One can refer to the state of the art to find examples of embodiment of the inflatable floats and inflation systems of these floats.

In addition, the buoyancy system is provided with at least one control system 36 for controlling the inflators 35. This control system 36 is then connected to at least one inflator 35 to require inflation of the floats 25.

The control system 36 may be a conventional system.

This control system may however comprise a computer having for example a processor, a circuit integrated, a programmable system, a logic circuit, these examples not limiting the scope given to the term "calculator".

This calculator can be optionally armed by an activation means 37 that can be operated by an individual. The activation means may have at least one position to make the buoyancy system active. Thus, the buoyancy system can be inhibited in certain situations, for example when the aircraft does not fly over a liquid surface.

The computer can determine whether predetermined inflation conditions are fulfilled, and can activate, if necessary, the inflators 35. For example, a selection means 61 that can be controlled by an individual makes it possible to transmit to the computer an order for inflating the external floats and / or interiors. The expression "means of selection" can designate a button, a touch screen, a voice control means, a keyboard or a pointer making it possible to manipulate computer means ...

Similarly, at least one immersion sensor 62 can detect the presence of water, and if necessary transmit to the computer an inflation order of the floats.

Other known systems can be used to inflate the floats, for example depending on the ground speed vector of the aircraft.

Regardless of the nature of the floats, each float 25 is movable in elevation by being attached to an elevation guidance system.

The guidance system of a float may be a system possibly guiding the floats in rotation and / or in translation.

The guidance system of a float can thus be a translation guide system which comprises at least one rail 41 fixed to a coating 550 of the cell, each rail 41 cooperating with a slider 45. For example, each float 25 is then connected to at least one slide 45 by ropes 42 or fittings for example.

Therefore, each float 25 can perform an elevational translation of a position called "lower position POS1" visible on the figure 1 to a position called "POS2 top position" which is not visible on this figure 1 .

The figure 2 illustrates an aircraft equipped with two pairs of floats. Only the left floats 31 present on the left side 6 of the aircraft are visible.

Each float 25 is then connected to the cell by at least one slide cooperating with a rail. In particular, figure 2 has floats 25 connected to two slides respectively engaged with two rails 41. The two rails can then be arranged longitudinally on either side of the door frames, or portholes 110.

In the lower position POS1, each float has a center of gravity CG substantially located in the lower part 7 of the aircraft. This center of gravity CG is then contained in a horizontal plane 200 which is perpendicular to the anteroposterior plane 100 and the gravity when the aircraft rests on the ground. Each lower plane 200 is then located under a median plane 250 separating in elevation the lower portion 7 and the upper portion 8.

In its lower POS1 position, a float 25 is optionally located at least partially under a porthole 110 so as not to close this porthole.

The figure 3 illustrates floats 25 in their upper positions POS2.

In the upper POS2 position, each float has a center of gravity CG substantially located in the upper part 8 of the aircraft. This center of gravity is then contained in a horizontal upper plane 300 parallel to the lower plane 200 of this float. Therefore, the upper plane 300 overlooks the lower plane 200.

In its upper POS2 position, a float 25 is optionally located at least partially above a porthole 110 so as not to close this porthole.

As a result, the buoyancy system comprises floats that can move in translation from a lower position POS1 to an upper position POS2

The displacement of the floats is, however, only possible under certain predetermined conditions.

Therefore and with reference to the figure 1 , the buoyancy system 20 comprises for each float 25 a blocking system 40. The blocking system 40 has the function of blocking by default each float 25 in the lower position POS1. In addition, the locking system 40 has the function of unblocking in a predetermined condition each float present on a single side of the aircraft 1 in order to block it in its upper position POS2.

When this predetermined condition occurs, each left float 31 or right float 32 is then released to reach its upper position POS2.

With reference to the figure 1 , the locking system 40 comprises a latch 46 called "lower latch 47" by rail 41 for holding a float 25 in the lower position POS1. Each lower latch 47 can be locked in a locked position and unlocked remotely.

Similarly, the locking system 40 comprises at least one lock 46 called "upper lock 48" for holding a float 25 in the upper position POS2.

In addition, the locking system 40 comprises a processing unit 60 connected to an activation system 63. The processing unit 60 then communicates with each lower lock 47 to allow the movement of a float 25 from the lower position POS1 to the upper position POS2 on request of the activation system 63.

This movement is irreversible without manual action of an individual on each upper lock 48.

Therefore, the processing unit 60 may have for example a processor, an integrated circuit, a programmable system, a logic circuit, these examples not limiting the scope given to the term "processing unit".

The processing unit 60 and the control system 36 mentioned above may represent a single electronic unit. Such an electronic unit may comprise at least one processor or equivalent and a memory, code segments stored in the memory belonging to the processing unit and code segments stored in the memory.

Furthermore, the activation system 63 may comprise a control member 64, operable by a pilot, connected to the processing unit 60. This control member 64 allows a pilot to maintain each float 25 in its lower position. POS1 is to allow the displacement of each float 25 present on one side of the aircraft 1 to its upper position POS2.

For example, the control member 64 is a rotary knob with three positions respectively for holding the floats in their lower positions, to allow the displacement of the left floats in their upper positions, or to allow the displacement of the right floats in their positions. higher.

Maneuvering the control member 64 then represents a predetermined condition allowing the translation of certain floats.

Complementarily or alternatively, the activation system 63 may comprise a measurement system 65 which measures a roll angle ROL of the aircraft 1. The measurement system 65 may comprise an inclinometer or an inertial unit for example.

The measurement system 65 then transmits a signal representative of this roll angle to the processing unit.

If an angle of roll upper or lower threshold is reached, the processing unit can allow the translation of some floats.

The detection of the presence of such a roll angle then represents a predetermined condition allowing the translation of certain floats.

The Figures 4 to 8 detail the realization of a locking system 40.

With reference to the figure 4 , a float 25 is connected to the cell 2 by at least one rail 41. The envelope 30 of the float 25 is then fixed to a slider 45 by ropes 42.

With reference to the figure 5 a rail 41 may be a C-shaped rail. Such a rail has a bottom wall 411 secured to the cell. In addition, the rail has two side walls 412 each extending from the bottom wall 411 to reach a flange 413. The two flanges 413 are substantially parallel to the bottom wall, and are separated from one another. other by empty space 414.

The slide 45 then comprises a rod 451 carrying at least one wheel 452, or even the ropes 42. For example, the rod 451 carries two wheels 452, each wheel 452 extends disposed transversely between the bottom wall 411 and a rim 413. The slide also comprises a contact plate 453 integral with the rod 451 to cooperate with each latch interference form.

With reference to the figure 4 , the rail further has a lower abutment wall 420 blocking the downward translation of the slider 45, and an upper abutment wall 430 blocking the upward translation of the slider 45.

Furthermore, a lock 46 called "lower latch 47" and a lock called "upper latch 48" are arranged in the rail or near the rail to lock the slide respectively in a lower position or an upper position.

At least one lock 46 or each latch 46 of a locking system comprises a valve 49. This valve is rotatable around a longitudinal axis with respect to the coating of the cell. Thus, each valve can rotate to project from a coating 550 of the aircraft 1 in a POS3 locking position visible on the figure 4 in order to block the float 25, or to be retracted at least partially in the coating 550 in an unlocking position to unlock the float.

This valve 49 comprises a plate or equivalent having substantially a triangle shape.

This valve is then provided with a vertical face 53, an inclined face 50 and a flat face 51. The valve is further articulated to the cell by a hinge 52 present at the junction of the vertical face and of the inclined face.

This inclined face 50 has a first inclination acute α1 with respect to a direction of extension D1 of displacement of the float 25. Therefore, the plane face 51 has a second inclination α2 with respect to the extension direction D1 greater than the first inclination α1. For example the second inclination is substantially equal to 90 degrees when the valve protrudes outside the coating.

The first inclination of the inclined face then has the function of causing the rotation of the shutter by interference of shapes with the slider when a predetermined condition is fulfilled. Conversely, the second inclination tends to prevent the slider from returning to its initial position.

In addition, the latch 46 comprises a spring 55 exerting a force on the valve 49 to tend to hold the valve 49 in the locking position POS3. This spring can extend between a fixed partition 56 of the aircraft and the vertical face 53 of the valve.

Furthermore, the valve 49 may have a stop 57 for stopping a rotation of the valve 49 from the unlocking position to the locking position POS3 when the locking position POS3 is reached. The abutment can for example enter for this purpose in contact with the bottom wall of the rail, a rim of the rail, or even with the coating 550 of the cell.

Furthermore, a latch 46 and in particular a lower latch 47 may include an electrical immobilizer 58. This immobilizing member is for example connected to the processing unit 60 to prevent or allow a rotation of the valve 49.

The figures 6 and 7 show embodiments of a lower latch 46.

According to the realization of the figure 6 , the immobilizing member takes the form of an electric lock 581 movable in rotation. The electric strike is then articulated to the coating 550 of the cell.

Following a landing, the thrust exerted by the water on the float tends to induce a translation of the slide according to the arrow F1. The slide then comes into contact with the inclined face of the valve 49.

However, in the position shown in solid lines, the electric strike then prevents the rotation of the valve. The valve is thus maintained in its blocking position.

As a result, when the slider and the float 25 are in their lower positions, the slider is locked between the lower abutment wall 420 and the lower latch valve 47.

If a predetermined condition occurs, the processing unit allows the rotation of the electric strike, for example by electrically supplying the electric strike.

As a result, the electric strike 581 performs a rotation F2 due to the force exerted by the valve on this striker. The valve performs in parallel a rotation F3 to reach the unlocking position POS4 shown in dashed lines by compressing the spring 55. This valve is thus at least partially retracted into the cell.

Therefore, the valve no longer impedes the translation of the slider 45. The slider 45 and the float 25 then move in translation along the rail 41.

When the slider is no longer in contact with the valve, the spring 55 exerts a force on the valve which tends to bring the valve in its locking POS3 position through a rotation F4. Whatever the freedom of movement offered to the electric lock, the slider can no longer return to the lower position, at least without human intervention.

According to the realization of the figure 7 , the immobilizing member takes the form of a latch 582 movable in rotation. The latch 582 is then carried by a motor 583 fixed to the coating 550 of the cell for example.

This latch has the function of wedging an abutment 57 of the valve, for example against the coating 550 of the cell.

Following a landing, the thrust exerted by the water on the float tends to induce a translation of the slide according to the arrow F5. The slide then comes into contact with the inclined face 50 of the valve.

However, in the position shown in solid lines, the latch 582 then prevents the rotation of the valve. The valve is thus maintained in its POS3 locking position.

As a result, when the slider and the float 25 are in their lower positions, the slider is locked between the lower abutment wall 420 and the lower latch valve 47.

If a predetermined condition occurs, the processing unit orders the rotation F6 of the latch 582, for example by electrically supplying the motor 583.

The valve performs parallel rotation F7 to then reach the unlocking position POS4 shown in dashed lines by compressing the spring 55. This valve is thus at least partially retracted into the cell.

Therefore, the valve no longer impedes the translation of the slide. The slide and the float 25 then move in translation along the rail 41.

When the slider is no longer in contact with the valve, the spring 55 exerts a force on the valve which tends to bring the valve back to its POS3 locking position through a rotation F8. The slide can not then return to the lower position, at least without human intervention.

Independently of the realization of the lower lock, when the slide is released by the lower lock, the buoyancy force exerted on the float and the depression of the aircraft in the water jointly induce the movement of the slide along the rail.

With reference to the figure 8 the slider 45 consequently reaches the upper latch 48.

The slider 45 then exerts a force on the valve 49 of the upper latch 48. The valve 49 makes a rotation F9 to then reach the unlocking position POS4 shown in dashed lines by compressing the spring 55. This valve 49 is thus at least partially retracted into the cell.

Therefore, the valve 49 no longer impedes the translation of the slide. The slide and the float 25 then move in translation along the rail 41 to the upper stop wall 430.

When the slider 45 is no longer in contact with the valve 49, the spring 55 exerts a force on the valve 49 which tends to bring the valve back to its locking position POS3 through a rotation F10. The slider can then no longer return to the lower position, at least without human intervention on the valve 49.

The Figures 9 to 11 illustrate the process implemented by the invention.

With reference to the figure 9 when an aircraft 1 lands on a liquid surface 900, the floats 25 are deployed to maintain the afloat of the aircraft 1.

In the context of inflatable floats, the floats may be inflated in flight prior to landing, or after landing.

Each float 25 is then in its lower position POS1.

If the sea is for instance agitated and with reference to figure 10 , the activation system may require the movement of each float present on one side of the aircraft to its upper position.

For example, the pilot or a system for measuring a roll angle can require such a displacement.

According to the example of the figure 10 , each left float 31 is released to allow its movement to its upper position.

The displacement of the left floats induces an increase in the roll angle ROL of the aircraft which does not seem reasonable because part of the cabin Z2 is then immersed.

However, the Applicant notes that the stability of the aircraft on the aircraft is then maximal.

In addition, this inclination in roll makes it possible to maintain a zone Z1 of the cabin outside the water

With reference to the figure 11 if the aircraft turns, this aircraft may still have interesting stability. In addition, part of cabin Z3 is still out of the water. The occupants of the aircraft can then detach themselves from their seats to allow their breathing.

Naturally, the present invention is subject to many variations as to its implementation. Although several embodiments have been described, it is well understood that it is not conceivable to exhaustively identify all the possible modes. It is of course conceivable to replace a means described by equivalent means without departing from the scope of the present invention.

For example, the figures describe an aircraft equipped with left and right floats likely to move in translation. Nevertheless, according to one variant, only the floats present on a given side can move. This variant tends to lighten the aircraft.

Claims (14)

1. An aircraft (1) provided with an airframe (2) which extends longitudinally along an anteroposterior plane (100), said airframe (2) extending transversely from a left-hand side (5) towards a right-hand side (6) and in elevation from a bottom (700) towards a top (800), said aircraft comprising a buoyancy system (20), the buoyancy system (20) being provided with at least one pair of two floats (25), two separate floats (25) of a pair being arranged transversely on either side of said anteroposterior plane (100),
   characterised in that, said buoyancy system (20) being provided for each float (25) with at least one slide (45) which is mounted to slide relative to a rail (41), each rail (41) extending in elevation, each slide (45) being attached to a corresponding float (25), each float (25) is mobile in elevation from a lower position (POS1) towards an upper position (POS2) by each slide fastened to the float sliding along a rail, a centre of gravity (CG) of each float (25) being present in an upper plane (300) perpendicular to the anteroposterior plane (100) in the upper position (POS2) and in a lower plane (200) in the lower position (POS1), the lower plane (200) being parallel to the upper plane (300) and being located below the upper plane (300) when the aircraft (1) has a zero angle of roll (ROL), said buoyancy system (20) comprising for each float (25) a blocking system (40) for blocking, by default, each float (25) in the lower position (POS1) and for blocking the floats present on a single side of the aircraft (1) in the upper position (POS2) in a predetermined condition.
2. An aircraft according to Claim 1,
   characterised in that, said airframe (2) extending in elevation from a lower portion (7) provided with said bottom (700) towards an upper portion (8) provided with said top (800), said lower position (POS1) is located in a lower portion (7) of the aircraft, said upper position (POS2) being located in the upper part (8) of the aircraft.
3. An aircraft according to any one of Claims 1 to 2,
   characterised in that said buoyancy system (20) is provided, for each float (25), with two slides (45) mounted to slide respectively relative to two rails (41), each rail (41) extending in elevation, each slide (45) being attached to a corresponding float (25).
4. An aircraft according to any one of Claims 1 to 3,
   characterised in that said blocking system (40) comprises at least one latch (46), referred to as "lower latch (47)", intended to hold a float (25) in the lower position (POS1), said blocking system (40) comprising at least one latch (46) [sic], referred to as "upper latch (48)", intended to hold a float (25) in the upper position (POS2), said blocking system (40) comprising a processing unit (60) linked to an activation system (63), said processing unit (60) controlling at least each lower latch (47) in order to permit the displacement of a float (25) from the lower position (POS1) towards the upper position (POS2) at the request of the activation system (63), said upper latch having the function of making said displacement irreversible without manual action by an individual on each upper latch (48).
5. An aircraft according to Claim 4,
   characterised in that said activation system (63) comprises a control member (64) which can be operated by a pilot, enabling a pilot to choose to hold each float (25) in its lower position (POS1) or to permit the displacement of each float (25) present on a single side of the aircraft (1) towards its upper position (POS2).
6. An aircraft according to any one of Claims 4 to 5,
   characterised in that said activation system (63) comprises a measurement system (65) which measures an angle of roll (ROL) of the aircraft (1).
7. An aircraft according to any one of Claims 4 to 6,
   characterised in that at least one latch (46) comprises a rotary flap (49) articulated to the airframe (2) in order to effect rotation so as to protrude from a skin (550) of the aircraft (1) in a blocking position (POS3) in order to block the float (25) or so as to be retracted at least partially into said skin (550) in an unblocking position (POS4) in order to unblock the float (25).
8. An aircraft according to Claim 7,
   characterised in that the rotary flap (49) is provided with an inclined face (50) and a planar face (51), the inclined face (50) having a first acute inclination (α1) relative to a direction of extension (D1) of displacement of the float (25) from the lower position (POS1) to the upper position (POS2), the planar face (51) having a second inclination (α2) relative to the direction of extension (D1) which is greater than the first inclination (α1).
9. An aircraft according to any one of Claims 7 to 8,
   characterised in that said latch (46) comprises a spring (55) which exerts a force on the flap (49) in order to tend to hold the flap (49) in the blocking position (POS3).
10. An aircraft according to any one of Claims 7 to 9,
    characterised in that said flap (49) comprises an abutment (57) for stopping rotation of the flap (49) from the unblocking position (POS4) towards the blocking position (POS3) when this blocking position (POS3) is reached.
11. An aircraft according to any one of Claims 7 to 10,
    characterised in that said latch (46) comprises an electric locking member (58) cooperating by shape interference with said flap (49) in order to prevent or permit rotation of the flap (49) at the request of a processing unit (60).
12. An aircraft according to any one of Claims 1 to 11,
    characterised in that said aircraft (1) comprises windows (110), a float (25) being located at least partially beneath a window (110) in the lower position (POS1) and at least partially above the window (110) in the upper position (POS2) in order not to mask said window (110) completely.
13. A buoyancy method for making an aircraft (1) which is provided with an airframe (2) which extends longitudinally along an anteroposterior plane (100) float, said airframe (2) extending transversely from a left-hand side (5) towards a right-hand side (6) and in elevation from a bottom (700) towards a top (800), said aircraft (1) comprising a buoyancy system (20), the buoyancy system (20) being provided with at least one pair of floats (25), two outer floats of a pair being arranged transversely on either side of said anteroposterior plane (100) on the outside (EXT) of the airframe (2),
    characterised in that said aircraft (1) is an aircraft (1) according to any one of Claims 1 to 12
    and in that the method comprises the following steps:

    - each float (25) of a pair is made to be mobile in elevation from a lower position (POS1) towards an upper position (POS2), each float being attached to at least one slide (45) which is rendered sliding relative to a rail (41) in order to permit the displacement of the float from the lower position towards the upper position,

    - each float (25) is held by default in a lower position (POS1), and

    - when a predetermined condition occurs, all the floats (25) present on a single side of the aircraft are arranged in the upper position (POS2).
14. A buoyancy method according to Claim 13,
    characterised in that the method comprises the following step:
    the floats (25) present on a single side of the aircraft are arranged in the upper position (POS2) at the request of a pilot or when an angle of roll (ROL) of the aircraft (1) reaches a predefined threshold.

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